1. Field of the Invention
The present invention relates to a changeover device and method for changing over winding of a web. More particularly, the present invention relates to a changeover device and method for changing over winding of a web, in which the web with an extremely small thickness can be treated safely without breakage, wrinkles or other damages.
2. Description Related to the Prior Art
There are various types of web winders for winding a web or continuous material about a spindle, for example paper, plastic film or the like. It is important in the web winder to wind the web continuously without stopping its flow, in view of time required for the operation, management of the production, and the like.
JP-A 8-157112 and JP-A 11-171377 disclose an example of the web winder for automatically winding the web traveling continuously. JP-A 8-157112 cuts the web partially wound about a first spindle. After this, an upstream web section from the web is changed over to a second spindle, which continuously winds the upstream web section. For the purpose of winding the web about the second spindle, an end of the upstream web section is attached by a sheet applicator to a leading sheet or guide leader extending from the second spindle. For suitable attachment, the sheet applicator must move at an equal speed to that of the web. According to JP-A 8-157112, the sheet applicator is stationary in the web winder. Part of the web being transported near to the sheet applicator is retained in a temporary manner by a nipping mechanism, for the purpose of the attachment. An accumulator is positioned upstream from the nipping mechanism, and stores the web transported during the attachment, so as to keep a continuous flow of the web.
In the web winder in JP-A 11-171377, there is no use of the accumulator. The web winder automatically winds the web continuously transported. A nipping roll and a spindle nip the web. A portion of the web is cut on a cutting line downstream from the nipping position. At the same time as the cutting, the web is attached to the spindle with double-sided adhesive tape previously adhered to the spindle, for the purpose of changeover operation. Then rotation of the spindle winds the web.
However, a problem arises in the sue of the accumulator of JP-A 8-157112. When the web is moved at a high speed, a required stored amount of the web increases. The web winder may be very complicated and have a remarkably large size. It is likely that no suitable tension is applied to the web when the accumulator is operated. Wrinkles may occur in the web.
In JP-A 11-171377, the web is cut at a cutting point that is in front of a position of attaching the adhesive tape. A front end of the web remains free in front of the attaching position. As the web is remarkably thin and has a low rigidity, the web may have wrinkles or folds in contact with the spindle.